Pilot valves are usable for control of a flow of fluid so as to control main valves, and for control of the opening degree of the main valves. A microvalve is a typical one of the pilot valves usable for control of the main valves. By control of a pilot microvalve, a corresponding flux of controlled fluid is obtained, and with the controlled fluid, a precise control of the opening degree of a main valve can be achieved.
In general, a microvalve refers to a micro-electromechanical system (MEMS) machined by using microelectronics processes. In the microvalve machined by using microelectronics processes, the size of a core member (an actuator) is usually on the order of micrometer. Mechanical movement of the actuator is achieved by means of applying an electrical excitation to the actuator. In addition to this, the microvalve may further include other component that is produced by or not by micro-machined processes.
At present, there have been a variety of microvalve structures useful for control of the fluid flow in fluid passages in microvalves.
FIGS. 1 and 2 schematically illustrate an existing microvalve device. The microvalve device is composed of an actuator (not shown) and a movable member 20. The movement of the movable member 20 is controlled by the actuator, and a controllable movement of the actuator can be realized by means of applying an electrical signal to it. The movable member 20 has a plurality of through holes therein. Through movement of the movable member, the degree to which fluid ports 31 and 33 in the microvalve are opened can be controlled, so as to control the fluid flux outflowing from the microvalve (the flow of fluid in a chamber of the microvalve), and in turn, a main valve is controlled.
A typical actuator is constituted by a beam, one end of which is fixed, and a movable member is connected to the other end of the beam. Adequate displacement and driving force are generated by the actuator when it is driven by an electric signal, for driving the movable member to slide in a chamber, so that the flow status of fluid at a control port is changed. Thus, a purpose of controlling the main valve is achieved. For example, FIG. 1 and FIG. 2 illustrate different states in which the movable member 20 takes control of the fluid flow at different locations, respectively. Arrows in the figures denote the flow direction of fluid.
Size of the actuator and power of an input electric signal are jointly determined by the displacement that the movable member needs to move, amplifying function of the microvalve on the displacement and the required driving force.